A common equation used in business is a demand equation. It expresses the relationship between the unit price of some commodity and the quantity demanded. In the​ equation, p represents the unit price and x represents the quantity demanded in thousands. A company sells desk lamps and has found that the demand equation for a certain style of desk lamp is given by the equation p equals negative x squared plus 23. Find the demand for the desk lamp if the price is ​$7 per lamp.